Mitsubishi-Forums.com - The UNOFFICIAL Mitsubishi Community This site is NOT affiliated in any way with Mitsubishi or any of it's subsidiaries. Our goal is to provide Mitsubishi owners an information outlet - a means to communicate with other Mitsubishi owners. It is simply a community where fans and owners can get the right information for tuning, customization and general discussions on anything about Mitsubishi. You'll find the answer to almost any question about your Mitsubishi in this site. If not, simply join and ask! We have many willing expert members just waiting to answer your questions.

My 03 galant engine light went on for a while before I got the codes checked from Autozone. Did not expect to get two codes. Would really appriciate for any clues or suggestions about the two codes.

Code 1. P0135, heated oxygen sensor, bank 1, sensor 1. For this code I think I'll have to test the oxygen sensor. My question is where it is located. From what I checked, sensor 1 should be the one that I can see easily when opening the hood, just in front of the engine and pops out. Is that right?

Code 2, P0740, TCC system malfunction. For this problem I really don't have much clue. I would really want to know how severe the problem is. is it just lowers the gas mileage or it can lead to other more serious damage to the transmision or other parts?

Oxygen sensor 1 ( yur car onlee has one bank since its a 4cyl) is the sensor on the exhaust manifold right above the exhaust manifold mounted catalytic converter . When yu have a code they usually have failed. Yu will waist yur time checking. If yu do not kno where its location is im not sure yull kno how to accurately check it, The heater element has likely failed in it which is common.

TCC (Torque Converter Clutch) meaning the Torque converter clutch is either likely not engaging , or partially engaging . Or the circuit is staying stuck defaulted on it. This can be due sumtimes to severly old transmission fluid , or low fluid levels restricting pressure for proper TCC operation.

Yu should change yur transmission fluid , and hopefully it may aid in correcting the situation. Otherwise yu may also be having an issue with the torque converter

Thanks a lot KiT TeUnG 2549 and SRSONE. I am now pretty sure where this sensor is and going to have it replaced. It haven't been changed after I bought this galant back in 2009, when it has 103000 miles on it.

For the TCC code I am also considering changing transmission fluid, although this galant still drives good and did not show abnormal gearing when I accelerate to 60 mph. However from what I checked online it seems that changing transmission fluid is not something that you can do without a garage and tons of special tools. So I wonder if you guys have an idea how much would it cost to have this job done in a service shop??